Structure for electroerosive machining with rotating tubular electrodes

ABSTRACT

Structure for and a method of electrical machining is disclosed. The structure includes electrical machining apparatus, a quickchange electrode supporting tool and means for rapidly and accurately securing the electrode-supporting tool to the electrical machining apparatus.

United States Patent Thomas J. O'Connor 100 Morgan Road, Ann Arbor.Mich. 729,584

May 16. 1968 June 29, 1971 Inventor Appl. No. Filed Patented STRUCTUREFOR ELECTROEROSIVE MACHINING WITH ROTATING TUBULAR ELECTRODES 3 Claims,10 Drawing Figs.

US. Cl 219/69 V, 77/22, 219/69 D Int. Cl 823p 1/08, 823p 1/04 Field ofSearch 219/69 R,

69 D, 69 E, 69 V, 69 F; 77/22 References Cited UNITED STATES PATENTSPorterfield 219/69 (V) Hyatt 77/22 Lindsay et a1 77/22 UXKurtzetal...... 219/69(V)X Williams 219/69 (D) Piotetal 2l9/69(E).Primary ExaminerR. F. Staubly Attorney-Whittemore, I-Iulbert & BelknapABSTRACT: Structure for and a method of electrical machining isdisclosed. The structure includes electrical machining apparatus, aquick-change electrode supporting tool and means for rapidly andaccurately securing the electrode-supporting tool to the electricalmachining apparatus.

PATENTEB Juuzelsn 3, 590.204

SHEET 2 or 3 10s 9 I 06100 8 NH W Ill! il 66 FIG.8

INV TOR THOMAS J- o'cow R BY WC M ATTORNEYS PATENIEU Juneels'n'" SHEET 3[IF 3 FIG.9

VFIGIO INVENTOR moms J. O'CONNOR ATTORNEYS STRUCTURE FOR ELECTROEROSIVEMACHINING WITH ROTATING TUBULAR ELECTRODES The quick-changeelectrode-supporting tool includes separate means for supporting aplurality of small diameter electrodes immediately adjacent each otherand means for rotating the electrode-supporting means. In onemodification the means for rotating the electrode-supporting meansincludes a driven endless ribbon engaged with opposite sides of adjacentelectrode-supporting means include a worm gear portion on each of theseparate electrode-supporting means and an elongated worm insimultaneous engagement with the worm gear portions, offset crankportions on the electrodesupporting means, a rotating disc and means foreccentrically connecting the rotating disc to the crank portions andchain and sprocket drive mechanisms.

The method of electrical discharge machining disclosed includes thesteps of supporting a plurality of small diameter electrodes in a lineand immediately adjacent each other, simultaneously rotating theelectrodes, moving the electrodes together toward a workpiece andproviding an electrical signal between the workpiece and electrode inthe presence of a dielectric.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to structure for and a method of electrical machining and refersmore specifically to a quickchange too] for supporting a plurality oflinearly closely spaced, small diameter electrodes adjacent each otherand simultaneously rotating the electrodes, whereby a plurality of smalldiameter, closely spaced openings may be machined in a workpiece inconjunction with electrical machining apparatus, and the method of useof the tool for electrical machining in conjunction with electricalmachining apparatus.

2. Description ofthe Prior Art In the past closely spaced linearlypositioned openings in a workpiece have generally been separatelymachined by a mechanical drilling operation. Such operation requires aplurality of separate positioning of a drill or workpiece and are infact impossible with many exotic metals due to the hardness thereof andthe small diameters of the openings required. Wherein simultaneousdrilling of such small diameter openings has in the past been attempted,the drill drive mechanisms have been particularly complicated and theoperations have generally been inefficient due to misalignment of and/orbreaking of the drills in use.

Similarly, in the past wherein small diameter closely spaced openingshave been electrically machined in conducting workpieces, the operationhas usually been accomplished by individually cutting the requiredopenings due to the difficulty of providing rotation of a plurality oflinearly positioned, closely spaced electrode-supporting structuressimultaneously. Such operation again requires individual setup time tomachine the adjacent openings relative to each other.

Structure for simultaneously electrically machining a plurality of smalldiameter openings closely spaced along a straight line whilesimultaneously rotating the cutting electrodes to provide improvedmachining in a quick-change tool attachment for electrical machiningapparatus has not in the past been provided.

SUMMARY OF THE INVENTION In accordance with the invention there isprovided a quickchange tool for electrically machining a plurality ofclosely spaced small diameter openings which may be linearly positionedwith rotating electrodes in conjunction with electrical machiningapparatus. 7

The tool includes means for rotatably supporting a plurality of smalldiameter electrodes in closely spaced linear relation and a plurality ofmeans including ribbon, worm and worm gear, eccentric crank, and chainand sprocket mechanisms for simultaneously rotating theelectrode-supporting means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of thestructure of the invention including a quick-change tool constructed inaccordance with the invention secured to electrical machining apparatusfor performing the method of the invention.

FIG. 2 is an enlarged, partly broken away front elevation view of thequick-change tool illustrated in FIG. 1.

FIG. 3 is a partly broken away, top view ofthe quick-change toolillustrated in FIG. 1.

FIG. 4 is an enlarged, partial section view of the quickchange toolillustrated in FIG. 1, taken substantially on the line 4-4 in FIG. 3.

FIG. 5 is a partly broken away, end elevation view of the quiclechangetool illustrated in FIG. 1, taken in the direction of arrow 5 in FIG. 3.

FIG. 6 is a front elevation view of a modification of the quick-changetool illustrated in FIG. 1.

FIG. 7 is a top view of the quick-change tool illustrated in FIG. 6.

FIG. 8 is an enlarged, partial cross section view of the modifiedquick-change tool illustrated in FIG. 6 taken substantially on the line8-8 in FIG. 7.

FIG. 9 is a longitudinal section view of another modification of aquick-change tool constructed in accordance with the invention.

FIG. 10 is a front elevation view of still another modification of aquick-change tool constructed in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, thestructure 10 for electrically simultaneously machining a plurality ofsmall diameter, closely spaced linearly positioned openings in a worlpiec'e 12 includes the electrical discharge machining apparatus 14 andthe quick-change tool 16. The method of use of.the structure 10 includesmoving the tool 16 toward the workpiece 12 while passing an electricalsignal between rotated electrodes 18 carried by the tool 16 and theworkpiece 12 in the presence of a dielectric.

Electrical discharge machining apparatus 14, including the mechanicalsection 20, servomechanism 28 and power supply 22, are well known, asindicated in the OConnor US. Pat. No. 3,222,494 and the references citedtherein. They will not therefore be considered in detail herein, exceptto indicate the operation thereof.

In operation, the mechanical section 20 of the electrical dischargemachining apparatus 14 supports quick-change tool 16 in the dovetailplaten structure 24 for controlled movement toward and away from theworkpiece l2 maintained in the dielectric tank 26 by the servomechanism28. The servomechanism 28 is energized in accordance with the signalpassed from the power supply 22 between the electrodes 18 and theworkpiece 12 secured to the grounded mechanical section 20 of theelectrical discharge machining apparatus 14.

The quick-change tool 16 is disclosed in more detail in FIGS. 2 through5. Tool 16 includes the steel base 30 having the opening 31, thesupporting plate 32 which is spaced from the base plate by spacers 33,the teflon bearing and guide plates 34 and 36 and the spacers 37therebetween, all secured together as shown by conventional means, suchas bolts (not shown). The drive motor 38 and dovetail member 40 are alsosecured to the base plate 30 in a conventional manner. 7

A plurality of separate electrode supporting means 42 are rotatablysuspended from the supporting plate 32 for rotation in and guidance bythe teflon plates 34 and 36. The electrode supporting means include ashaft 44 having a threaded opening 46 in the lower end thereof forreceiving a threaded electrode shank and having a threaded reduceddiameter 48 at the opposite end thereof. The shaft 44 passes through theguide openings 50 and 52 in the teflon plates 34 and 36, respectively,while the reduced diameter end 48 passes through the opening 54 in thesupporting plate 30. A sleeve 56 is threaded over the reduced diameterend 48 of the shaft 44 and is secured in place by the locking screw 58,whereby the shaft 44 is rotatably supported by the plate 32.

Spring means 60 is provided in conjunction with the electrade-supportingmeans 42 for electrically connecting the electrodes 18 secured to theelectrode-supporting means 42 with the power supply 22 of the electricaldischarge machining apparatus 14, as will be understood by thosein theart.

The drive means 62 for the electrode-supporting means 42, illustratedbest in FIGS. 2 and 3, includes the ribbon 64 which may be a typewriterribbon threaded over the guide rollers 66, 68 and 70 and alternatelyunder and over adjacent electrodesupporting means 42, so as to be indriving engagement with the opposite sides of the adjacentelectrode-supporting means. The ribbon 64 is further passed around thefriction drive member 72 which in turn is secured to the motor shaft 74for rotation therewith on energizing the motor 38.

The tension on the ribbon 64 may be adjusted by means of the adjustingscrew 76 threaded through the spacer 37 between the neoprene plates 3.4and 36. The ribbon guide 68 mounted on the member!!!) may therefore beadjusted to provide desired tension in the ribbon 64 through threadedengagement of the shank 82 secured thereto with the adjusting screw 76.

ln overall operation, as the quick-change 'tool 16 is moved toward theworkpiece 12, the electrodes 18 are rotated by means of the motor 38which may be energized from any convenient source of electricity todrive the typewriter ribbon 64. The openings produced by thequick-change tool 16 are geometrically correct due to the rotation ofthe electrodes and may be extremely close together, as for example on Ainch centers linearly, even though of very small diameter, as for example one thirty-second of an inch, without causing breakage of theelectrodes or without requiring complicated or particularly strongdriving mechanisms to rotate the electrodes, since no physical contactof the electrodes 18 is required with the usual high toleranceelectrical machining, such as in electrical discharge machining andelectrochemical machining.

The modified quick-change tool 84 illustrated in FIGS. 6, 7 and 8 againpermits simultaneous rotation of electrodes of very small diameter, suchas one thirty-second of an inch, linearly spaced adjacent each other atintervals of, for example, one quarter inch, with particularly simple,uncomplicated mechanism. As shown best in FIG. 6, the quick-change tool84 includes a base plate 86 to which the motor 88 and dovetail mountingmember 90 are secured. The steel supporting plate 92 is supported fromthe base plate 86 and spaced therefrom by the spacing blocks 94 and theneoprene plates 96 and 98 are secured together and spaced apart byspacers 100 at the opposite ends thereof, as shown best in FIG. 6.plates 86 and 92 and Plates 94 and plates 96 and 98 and spacers 100 aresecured together as shown by convenient means, such as adhesives, boltsor the like. 1

The electrode-supporting means 104 are rotatably mounted on the plate 92in linear alignment as before for rotation in and guidance by theneoprene plates 96 and 98. Each of the electrode supporting means 104 isin the modified quickchange tool 84 provided with a central worm gearportion 106, shown best in FIG. 8, which is engaged with the elongatedworm 108 rotatably supported in the spacers 100 and engaged with theworm gear portions of the electrode-supporting means 104.

The modified quick-change tool 112, shown in FIG. 9, includes theelectrode-supporting means 114 secured for rotation between the plates116 and 118 and guided by the guide member 120 secured to the plate 118at the opposite ends thereof, as shown. The electrode-supporting means114 are linearly positioned to provide closely spaced small diameterholes with an electrode secured thereto. Crank portions 122 on the upperend of electrode-supporting means 114 have offset ends 124 and 126. Theupper offset ends 126 are passed through openings in the drive plate 128for rotation therein on movement of the drive plate 128 which iseccentrically secured to the rotatable discs 130 and 132 by pivotstructure 134 and 136, respectively.

The motor is secured to the body 132 of the quick- 1 change tool 112.Body portion 142 of tool 112 provides spacing between the plates 116 and118 to produce the dielectric chamber 144 which will be consideredsubsequently. Motor 140 drives disc 132 through the rotatable shaft 146.A dovetail portion 148 is secured to the body portion 142 by convenientmeans, such as for example welding.

The electrode-supporting means 114 of the modified quickchange tool 112are hollow and receive hollow electrodes in the lower ends thereof. Aseal (not shown) is provided about each electrode-supporting means 114where it passes through the plates 116 and 118 and an opening 150extends transversely of the electrode-supporting means 114. Thus, inoperation, with dielectric passed into the chamber 144 through, forexample, a coupling 152 in the body 142, dielectric is passed throughthe openings 150 through the electrode-supporting means 114 and thehollow electrodes to maintain dielectric fluid between the electrodesand a workpiece.

In operation, as the quick-change tool 112 is advanced toward aworkpiece by the electrical machining apparatus, the motor 140 isenergized by a convenient source of electric energy to rotate the disc132 which in turn will move the plate 128 to rotate the disc 130 and theelectrode-supporting means 114. The electrode-supporting means 114 willthen, as before, rotate electrodes secured thereto to provide closelyspaced, small diameter, linearly positioned, openings with particularlysimple, efficient structure. Simultaneously the dielectric fluid passedinto the dielectric chamber 144 through the fitting 152 will passthrough the openings 150 in the hollow electrodesupporting means 114 andsubsequently through hollow electrodes supported thereby to maintaindielectric between the electrodes and a workpiece.

In the modification 154 of the quick-change tool illustrated in FIG. 10,the electrode-supporting structures 156 are supported for rotationbetween the plates 158 and 160 which are separated by spacers 162 and164.'The dovetail mounting portion 166 is conveniently secured to theplate 158 and electrodes 168 are secured to the electrode-supportingmeans 156 for movement toward and away from the workpiece 170.

The electrode-supporting structures 156 are again closely spaced inlinear arrangement and include sprocket means 172 secured thereto. Thesprocket means 172 are each engaged with a chain drive 174 which isdriven through motor 176, drive shaft 178 and sprocket 180. The motor176 is secured to the spacer 164 by brackets 182, as required.

Again with the tool structure 154, a plurality of small diameter,linearly positioned, closely spacedopenings may be electrically machinedon movement of the tool 154 toward the workpiece and the structure forrotating the electrodes is particularly simple, economical andefficient.

While one embodiment and modifications of the present invention havebeen considered in detail, it will be understood that other embodimentsand modifications are contemplated. It is the invention to include allembodiments and modifications as are defined by the appended claimswithin the scope of the invention.

What I claim as my invention is:

1. A quick-change tool for electrical machining comprising a base, meansfor supporting the base for movement toward and away from a workpiece,rotatable means secured to the base for supporting a plurality ofparallel small diameter electrodes immediately adjacent each other forrotation including a separate electrode holder for each electrode, motormeans secured to the base and means operable between the motor means andmeans for supporting the electrodes'for simultaneously rotating themeans for supporting the electrodes in the presence of a dielectric onenergization ofthe motor means including a rotatable disc secured to themotor for rotation about an axis parallel to the axis of rotation of themeans for supporting the electrodes, a rotatable disc secured to thebase of the quick-change tool for rotation about a separate axisparallel to the axis of the means for supporting the electrodes, aseparate crank member connected to each electrode holder includingparallel portions at the opposite ends thereof parallel to the electrodeholders and a single offset portion extending diagonally between theparallel ends thereof, one of the ends being connected to an associatedelectrode holder in axial alignment therewith and a plate having aplurality of openings therein for receiving the other ends of theseparate crank members and eccentrically pivotally connected to therotatably mounted discs at the opposite ends thereof whereby onenergizing the motor to rotate the one disc connected thereto the plateis caused to rotate in a parallel manner so that said other ends of thecrank members describe circles having centers on the longitudinal axisof the associated electrodes so that on movement of the tool toward aworkpiece with electrodes positioned in the means for supporting theelectrodes in the presence of a dielectric with opposite terminals of apower source connected to the electrodes and the workpiece electricalmachining of a plurality of closely spaced parallel small openings maybe accomplished in the workpiece. 1

2. Structure as set forth in claim 1 wherein the separate electrodeholders are hollow and the base further includes a pair of platesextending transversely thereacross defining a fluid chamber therewithand having a plurality of aligned parallel openings therethrough forrotatably receiving portions of the electrode holders within the chamberand openings extending radially through the electrode holder portionswithin the chamber whereby dielectric fluid within the chamber will passthrough the hollow electrode-holding means and out of hollow electrodessecured therein.

3. A quick-change tool for electrical discharge machining comprising abody portion which is a generally rectangular hollow member having aninwardly extending flange at the bottom thereof, a pair of platessecured to the body portion on opposite sides of the inwardly extendingflange defining a dielectric chamber therebetween, an opening extendinginto the chamber for feeding dielectric fluid thereinto, a guide portionsecured to the bottom of the quick-change tool adjacent the chambertherein, a plurality of aligned closely spaced small openings in theguide portion and plates of the quickchange tool, hollow electrodeholders secured in the openings for rotation therein, an openingextending radially through the electrode holders within the chamber ofthe quick-change tool for passing dielectric fluid in the chamber intothe electrode holders and out of hollow electrodes positioned therein, aseparate crank portion secured to each electrode holder, each having apair of parallel ends one of which is secured to the associatedelectrode holder axially thereof and a single transverse portionextending between the parallel ends thereof, a motor having a rotaryoutput shaft extending parallel to the electrode holders, a first discsecured to the motor shaft for rotation therewith, a second discpositioned on the body portion of the tool for rotation thereon, a thirdplate having a plurality of openings therethrough receiving the otherends of the crank portions of the quick-change tool and means connectingthe opposite ends of the third plate pivotally to the separate discseccentrically with respect to the axis of rotation thereof by the amountof the offset of the crank members whereby on energizing of the motorthe one disc is caused to rotate to move the third plate so as to rotatethe other ends of the crank members in circles having as centers ofrotation the longitudinal axis of the electrode holder associatedtherewith whereby the electrode holders are simultaneously rotated.

1. A quick-change tool for electrical machining comprising a base, meansfor supporting the base for movement toward and away from a workpiece,rotatable means secured to the base for supporting a plurality ofparallel small diameter electrodes immediately adjacent each other forrotation including a separate electrode holder for each electrode, motormeans secured to the base and means operable between the motor means andmeans for supporting the electrodes for simultaneously rotating themeans for supporting the electrodes in the presence of a dielectric onenergization of the motor means including a rotatable disc secured tothe motor for rotation about an axis parallel to the axis of rotation ofthe means for supporting the electrodes, a rotatable disc secured to thebase of the quick-change tool for rotation about a separate axisparallel to the axis of the means for supporting the electrodes, aseparate crank member connected to each electrode holder includingparallel portions at the opposite ends thereof parallel to the electrodeholders and a single offset portion extending diagonally between theparallel ends thereof, one of the ends being connected to an associatedelectrode holder in axial alignment therewith and a plate having aplurality of openings therein for receiving the other ends of theseparate crank members and eccentrically pivotally connected to therotatably mounted discs at the opposite ends thereof whereby onenergizing the motor to rotate the one disc connected thereto the plateis caused to rotate in a parallel manner so that said other ends of thecrank members describe circles having centers on the longitudinal axisof the associated electrodes so that on movement of the tool toward aworkpiece with electrodes positioned in the means for supporting theelectrodes in the presence of a dielectric with opposite terminals of apower source connected to the electrodes and the workpiece electricalmachining of a plurality of closely spaced parallel small openings maybe accomplished in the workpiece.
 2. Structure as set forth in claim 1wherein the separate electrode holders are hollow and the base furtherincludes a pair of plates extending transversely thereacross defining afluid chamber therewith and having a plurality of aligned parallelopenings therethrough for rotatably receiving portions of the electrodeholders within the chamber and openings extending radially through theelectrode holder portions within the chamber whereby dielectric fluidwithin the chamber will pass through the hollow electrode-holding meansand out of hollow electrodes secured therein.
 2. Structure as set forthin claim 1 wherein the separate electrode holders are hollow and thebase further includes a pair of plates extending transverselythereacross defining a fluid chamber therewith and having a plurality ofaligned parallel openings therethrough for rotatably receiving portionsof the electrode holders within the chamber and openings extendingradially through the electrode holder portions within the chamberwhereby dielectric fluid within the chamber will pass through the hollowelectrode-holding means and out of hollow electrodes secured therein. 3.A quick-change tool for electrical discharge machining comprising a bodyportion which is a generally rectangular hollow member having aninwardly extending flange at the bottom thereof, a pair of platessecured to the body portion on opposite sides of the inwardly extendingflange defining a dielectric chamber therebetween, an opening extendinginto the chamber for feeding dielectric fluid thereinto, a guide portionsecured to the bottom of the quick-change tool adjacent the chambertherein, a plurality of aligned closely spaced small openings in theguide portion and plates of the quick-change tool, hollow electrodeholders secured in the openings for rotation therein, an openingextending radially through the electrode holders within the chamber ofthe quick-change tool for passing dielectric fluid in the chamber intothe electrode holders and out of hollow electrodes positioned therein, aseparate crank portion secured to each electrode holder, each having apair of parallel ends one of which is secured to the associatedelectrode holder axially thereof and a single transverse portionextending between the parallel ends thereof, a motor having a rotaryoutput shaft extending parallel to the electrOde holders, a first discsecured to the motor shaft for rotation therewith, a second discpositioned on the body portion of the tool for rotation thereon, a thirdplate having a plurality of openings therethrough receiving the otherends of the crank portions of the quick-change tool and means connectingthe opposite ends of the third plate pivotally to the separate discseccentrically with respect to the axis of rotation thereof by the amountof the offset of the crank members whereby on energizing of the motorthe one disc is caused to rotate to move the third plate so as to rotatethe other ends of the crank members in circles having as centers ofrotation the longitudinal axis of the electrode holder associatedtherewith whereby the electrode holders are simultaneously rotated.